Medically reviewed by Prof. Dr. Aamer Nadeem Chaudhary, M.B.B.S., D.M.R.D., F.C.P.S. (Diagnostic Radiology), Consultant, Al-Nasar Lab & Diagnostic Centre. Updated September 2026.
Quick answer: A plain X-ray uses a very small radiation dose, comparable to a few days of the natural background radiation everyone receives. CT uses considerably more. Ultrasound and MRI use no ionising radiation at all. A single diagnostic X-ray taken before a pregnancy was known is almost never a reason for concern, and is not a reason to end a pregnancy.
Questions about a scan you have been referred for? Call 0300 0341944 and our radiology team can advise.
Which tests use radiation and which do not?
| Test | Ionising radiation | Relative dose |
|---|---|---|
| Ultrasound | None | Uses sound waves only |
| MRI | None | Uses a magnetic field and radio waves |
| Chest X-ray | Yes | Among the lowest doses in radiology |
| Limb X-ray | Yes | Very low, and far from the abdomen |
| Dental X-ray and OPG | Yes | Very low, and directed away from the body |
| Abdominal or spine X-ray | Yes | Higher than a chest X-ray |
| CT scan | Yes | Substantially higher than plain X-ray, varying by body part and protocol |
| Nuclear medicine scan | Yes | Varies by study, from an injected radioactive tracer |
How much radiation is a lot?
Some context helps more than numbers alone.
Everyone is exposed to natural background radiation every day, from the ground, from building materials, from food and from cosmic rays. It is unavoidable and it is part of ordinary life. A chest X-ray adds roughly what you would receive from the environment over a few days.
A CT scan is a different scale, delivering the equivalent of months to a couple of years of background exposure depending on the region scanned. That is why CT is not ordered casually, and why a radiologist will sometimes suggest ultrasound or MRI instead when either can answer the same question.
The honest position is this: the risk from any single diagnostic examination is very small, and it is almost always outweighed by the risk of not finding what is actually wrong. What deserves attention is repeated imaging over years, particularly repeated CT in younger patients.
What if I had an X-ray before I knew I was pregnant?
This is the question that causes the most distress, and the answer is reassuring.
A single diagnostic X-ray, particularly of the chest, limbs, teeth or head, delivers a dose to the uterus that is extremely small, in many cases effectively negligible because the beam is nowhere near the abdomen. It does not meaningfully raise the risk of miscarriage or birth defects, and it is not a medical reason to consider ending a pregnancy.
Even abdominal and pelvic examinations, which deliver more, fall well below the thresholds at which harm to a foetus has been demonstrated.
What you should do is straightforward: tell your obstetrician what examination you had and when. They can put it in context for your specific situation. If a CT of the abdomen or pelvis was involved, the radiology department can calculate the actual foetal dose, which is usually far lower than people fear.
What is used instead during pregnancy?
- Ultrasound is the first choice for almost everything in pregnancy. No radiation, and it answers most abdominal and pelvic questions
- MRI is used when more detail is needed. It uses no ionising radiation and is considered safe in pregnancy, though gadolinium contrast is generally avoided
- X-ray and CT are used only when genuinely necessary, for example after major trauma or when a life threatening condition is suspected. In those situations the risk of missing the diagnosis is far greater than the radiation risk
- Shielding is applied where practical, and protocols are adjusted to reduce dose
Always tell the radiographer if you are pregnant or think you might be, before the examination rather than after.
Are children more sensitive to radiation?
Yes, for two reasons. Growing tissues are more radiosensitive, and children have more years ahead in which any effect could theoretically appear.
This does not mean children should not have X-rays when needed. It means the dose should be matched to their size rather than an adult setting, alternatives should be considered first, and the examination should be justified.
In practice, paediatric imaging leans heavily on ultrasound and MRI wherever they can answer the question, with X-ray used freely for fractures and chest problems because the doses involved are small.
How radiation exposure is kept low
Three principles govern every examination performed in a properly run department:
- Justification. Every examination must have a clinical reason. A scan that will not change management should not be done
- Optimisation. The dose is kept as low as reasonably achievable while still producing a diagnostic image. Modern equipment adjusts automatically for body size, and low dose protocols exist for common studies such as CT for kidney stones
- Limitation. The field is collimated to the area of interest, shielding is used where appropriate, and unnecessary repeats are avoided
You can help with the third one. Bring your previous scans and reports. A great deal of repeat imaging happens simply because earlier images were not available for comparison.
Practical questions to ask before any scan
- What will this scan change about my treatment?
- Is there an alternative without radiation, such as ultrasound or MRI?
- Do I already have a recent scan that could be reviewed instead?
- If I need repeated imaging, can some of it be done with ultrasound?
These are reasonable questions and any radiologist will welcome them.
Imaging at Al-Nasar Lab
Al-Nasar Lab & Diagnostic Centre has served Lahore since 1996 and holds ISO 15189:2022 accreditation from the Pakistan National Accreditation Council. Because ultrasound, X-ray, CT and MRI are all available at our Johar Town campus, our radiologists can advise on the most appropriate test rather than defaulting to the one that happens to be available.
Related reading: is MRI safe and what to expect and MRI or CT, which do you need.
Contact us or find your nearest location.
Frequently Asked Questions
Is one X-ray dangerous?
No. A single diagnostic X-ray carries a very small risk, comparable to a few days of natural background radiation for a chest film, and it is outweighed by the benefit of an accurate diagnosis.
I had an X-ray before I knew I was pregnant. What should I do?
Tell your obstetrician which examination you had and when. A single diagnostic X-ray is not a reason to end a pregnancy, and for most examinations the dose to the uterus is negligible.
Does MRI use radiation?
No. MRI uses a magnetic field and radio waves, with no ionising radiation. The same applies to ultrasound.
How much more radiation is a CT than an X-ray?
Substantially more, varying by body region and protocol. That is why CT is reserved for questions a plain X-ray or ultrasound cannot answer.
Should I refuse a CT scan because of radiation?
No, not if it is clinically justified. A better approach is to ask what the scan will change, whether an alternative exists, and to bring previous imaging so nothing is repeated unnecessarily.
This article is for general information and is not a substitute for medical advice. Please discuss your results with a qualified doctor.
